Perhaps the most significant obstacle to overcome in successfully transfusing blood from a donor to a recipient is the detection of untoward immune responses. In particular, immune reaction of the recipient against the donor's blood can have life-threatening consequences for the recipient. Immune reactions between antigens present in the blood of the donor and antibodies against these antigens in the recipient can cause severe hemolysis, renal failure, and shock.
Examples of well-known and clinically significant antigens in blood are the A and B antigens of the ABO System. These antigens are present on the red blood cells which carry oxygen in the body. In order that transfusion occur successfully, it is imperative that the recipient not have antibodies directed to antigens present on donor blood cells. An immune reaction by the recipient of a transfusion of donor cells results in destruction of the donor cells with possible catastrophic damage to the kidneys and other organs.
Other antigens present on the surfaces of human red blood cells are also known; some of these can cause serious immune responses when transfused into patients with antibodies to them. The term "unexpected alloantibodies" is used to refer to antibodies to antigens on the surface of human red blood cells, other than the A, B or Rh antigens. American Association of Blood Banks Technical Manual, p. 333 (1993)("AABB Tech,. Manual"). While the A and B antigens are carbohydrate, the antigens to which unexpected alloantibodies are directed are proteins.
At present a number of systems of unexpected alloantibodies are known. The Lutheran, Kell, Duffy and Kidd systems are representative. Each of these systems has a number of allotypes. For example the Lutheran blood group system may display a or b antigens or both. Id. at 266. The Kell system includes at least three different antigens, which may be genetically linked. Id. at 268. The Duffy system includes two antigens, while the Kidd system includes two.
Because reaction between unexpected alloantibodies in the recipient and target antigens in the donor blood can have serious, clinical consequences, it is imperative to develop rapid and sensitive assays for unexpected antibodies. At present, unexpected antibodies are detected by laborious, and time-consuming testing of donor serum against panels of red blood cells with known antigenic determinants.
In the technique presently employed, the recipient's sera is mixed with human red blood cells known to display antigens from one or more blood group systems. The presence of an unexpected alloantibody bound to the test cells is demonstrated by observing hemagglutination following addition of an antibody to human immunoglobulin. Because the unexpected alloantibody could bind to any of a number of different antigens present on the test red blood cells, identification of the particular antigen to which an unexpected alloantibody is directed requires that the recipient's serum be tested against samples of red blood cells which display different combinations of antigens. When more than one unexpected alloantibody is present in the serum of the recipient, the analysis becomes complex, necessitating study of multiple panels of red blood cells. AABB Manual, pp. 340-43. The sequential testing of the serum sample of a recipient against different combinations of test cells (referred to as panels) is expensive, time consuming and laborious.
The subject of this application is a novel assay which obviates much of the time-consuming panel testing of the prior art method. The invention takes advantage of monoclonal antibodies directed to the known antigens to which unexpected alloantibodies are directed.